Figure 1. Overall association of metabolic syndrome with COPD risk.

Abbreviations: 95% CI, 95% confidence interval; COPD, chronic obstructive pulmonary disease; OR, odds ratio. OR is denoted by the center of a solid diamond, and the length of solid line cross this diamond denotes its 95% CI. The hollow diamond with a vertical broken line denotes overall risk estimate. The solid vertical line is set at the null value (OR = 1.0).